1. Field of the Invention
The present invention relates to a piezoelectric device including a piezoelectric element to which an elastic conductive member is fixed, and to a piezoelectric switch provided with the same.
2. Description of the Related Art
Conventionally, there have been an electric generator, which excites a piezoelectric element and allows it to vibrate freely to generate electricity (for example, refer to patent document 1), and a switching circuit, which includes such an electric generator (for example, refer to patent document 2). The above electric generator causes a piezoelectric body to expand and contract by bending a metal plate to which a polarized piezoelectric body in a thin plate-like shape is joined, and generates a voltage using a piezoelectric lateral effect. Therefore, either surface of the plate-shaped piezoelectric element has to be restricted by the metal plate. As specific structures, the following electric generators are now in practical use; i.e., a unimorph type, in which a plate-shaped piezoelectric element provided with electrodes at both sides is fixed to one surface of a metal plate; and a bimorph type, in which a similar piezoelectric element is fixed to both surfaces of a metal plate. A piezoelectric element and a metal plate are generally joined using a thermosetting resin in a heated state. Therefore, the metal plate often employs a material having the same level of low coefficient of thermal expansion as that of the piezoelectric element.
On the other hand, a piezoelectric actuator has been known, which has the same structure as that of the above electric generator and utilizes an inverse piezoelectric effect. In such piezoelectric actuators, some actuators have a structure in which a piezoelectric body is formed on a substrate having a thermal expansion coefficient greater than that of the piezoelectric body to reduce tensile stress within the piezoelectric body (for example, refer to patent document 3). By employing such a structure, the piezoelectric actuator preserves mechanical strength of thin film of the piezoelectric body to prevent the film from being cracked or broken due to the tensile stress.    [Patent document 1] Japanese Patent Application Laid-Open No. 2003-7491    [Patent document 2] Japanese Patent Application Laid-Open No. H7-49388    [Patent document 3] Japanese Patent Application Laid-Open No. 2004-146640